Cerebellum, Basal Nuclei & Extrapyramidal Systems PDF

Cerebellum, Basal nuclei & Extrapyramidal system Class Year 1, Semester 2 Lecturer DR. VIJAYALAKSHMI S B Department of Anatomy Email id: [email protected] Date 12-11-2024 1 Learning Outcomes Describe...

Cerebellum, Basal nuclei & Extrapyramidal system Class Year 1, Semester 2 Lecturer DR. VIJAYALAKSHMI S B Department of Anatomy Email id: [email protected] Date 12-11-2024 1 Learning Outcomes Describe the structure of cerebellum Discuss the mechanisms involved in control of balance and coordination Discuss cerebellar disease in relation to the anatomy of the region Identify parts of the basal nuclei Recognise the relationship of the anatomy to clinical problems e.g. Parkinson’s disease, Huntington’s disease  3 General Organization of Motor System  4 “Cerebellum”= Little brain In posterior cranial fossa Covered by tentorium cerebelli  5 Functional connections of cerebellum Connected with rest of the nervous system through highways “Peduncles”: Superior peduncle with midbrain Middle peduncle with pons Inferior peduncle with medulla oblongata 6  7 Divisions of cerebellum - Multiple ways A. Anatomical divisions into lobes: 1. Anterior 2. Posterior/Middle 3. Flocculonodular B. By anatomical connections: C. By Functions: 2  8 Divisions of cerebellum - Multiple ways B. By Functions: 1. Vestibulocerebellum 2. Spinocerebellum 3. Cerebrocerebellum D. By evolution: 1. Vestibulo Spino Cerebro  9 Divisions of cerebellum- Multiple ways A. Anatomical divisions into lobes: 1. Anterior 2. Posterior/Middle 3. Flocculonodular B. By Functions: 1. Vestibulocerebellum 2. Spinocerebellum 3. Cerebrocerebellum C. By evolution: 1. Archicerebellum PALEO PALEO 2. Paleocerebellum NEO 3. Neocerebellum ARCHI  10 Functional Divisions 1. FN lobe (Vestibulocerebellum): Deep cerebellar nucleus – Fastigial Interconnected with vestibular nuclei; Controls posture, balance, coordinated eye movements Lesion: Flocculonodular lobe syndrome Nystagmus + loss of balance + disturbed gait Nystagmus (rhythmic oscillation of eyes), posture problems, Wide ataxic gait. Patient tends to fall towards the affected side (Truncal ataxia)  11 SUMMARY OF MAJOR EFFERENTS FROM CEREBELLUM: Origin Pathway Function Disorder Flocculo nodular Projects to Coordination of Disturbed gait lobe via Fastigial vestibular posture, bilateral (Wide ataxic gait); nucleus nucleus & proximal and truncal loss of balance reticular muscle tone and eye (truncal ataxia) formation movements and nystagmus. They tend to fall to the lesion site. No ataxia in limbs. Inferior peduncle 12  13 Functional Divisions 2. Spinocerebellum Deep cerebellar nuclei – Globose & Emboliform Vermis & paravermis input from spinal cord; Maintains posture and muscle tone Lesion: Anterior lobe syndrome Nystagmus + loss of balance + disturbed gait  14 SUMMARY OF MAJOR EFFERENTS FROM CEREBELLUM: Origin Pathway Function Disorder Vermis and Spinal cord Ipsilateral Truncal and limb Paravermis via via red coordination of ataxia on the Interpositus nucleus posture, distal ipsilateral side. nucleus Ipsilateral muscle tone and eye movements Superior peduncle  15 Functional Divisions 3. Cerebro/Neo-cerebellum Deep cerebellar nucleus - Dentate Principal input from cerebral cortex to lateral hemisphere; Concerned with coordination, planning, and execution of movements Gives feedback to the motor cerebral cortex to correct movement errors Lesion: Posterior lobe syndrome – Limb ataxia Incoordination + unsteady gait no sensory deficit no muscular weakness Dysmetria, dysdiadochokinesis, intentional tremor  16 SUMMARY OF MAJOR EFFERENTS FROM CEREBELLUM: Origin Pathway Function Disorder Lateral region Dentothalamic Planning of Limb ataxia, intention via Dentate pathway movements tremor, dysmetria, nucleus (Cortex via dysdiadochokinesia. ventrolateral Ipsilateral side. thalamic nucleus) – Contralateral cerebral cortex Superior peduncle  EXAMPLE PATHWAY: CEREBROCEREBELLUM INPUTS: FROM Pre & Post-central gyrus Pathway: Frontopontine fibres Pontine nuclei Pontocerebellar fibers Cerebellar hemispheres Cerebellar nuclei OUTPUTS: To Pre-central gyrus Pathway: Superior cerebellar peduncle Ventral lateral nucleus of thalamus Precentral gyrus MOTOR PATHWAY Pathway: Precentral Gyrus (standard) DOUBLE DECUSSATION! (cerebellar output and UMN) EFFECTS ARE IPSILATERAL  18 Outflow pathways from the cerebellar cortex to the cerebral cortex and red nucleus  19 Deep Cerebellar nuclei Found within the white matter & represent the output nuclei of the cerebellum From medial to lateral, these nuclei are: 1. Fastigial nucleus – associated with the Archicerebellum and deals with balance & equilibrium 2. Interposed nuclei (Globose and Emboliform) – associated with the Paleocerebellum, deal with walking & arm movements 3. Dentate nucleus – most lateral & largest, part of Neocerebellum and is associated with highly skilled movements  20 Deep Cerebellar nuclei Receive inputs from incoming and outgoing neurons of cerebellum (Like “Toll gate”) Modulate the influence of cerebellum on rest of the nervous system  21 2. Blood supply to Cerebellum Vertebrobasilar artery  22 Vascular territories of cerebellar arteries DORSAL SURFACE OF Superior cerebellar (SCA) CEREBELLUM Anterior inferior cerebellar (AICA) Posterior inferior cerebellar (PICA) VENTRAL SURFACE OF NOTE VASCULAR PROBLEMS: CEREBELLUM 1. Most common is SCA and PICA. 2. Mostly SCA infarcts present with PURE CEREBELLAR signs 3. PICA & AICA have sensory and motor deficits due to brainstem involvements as well LESIONS Midline lesion Vestibulocerebellum / spinocerebellum Nystagmus + loss of balance + disturbed gait Lateral lesion Cerebrocerebellum Incoordination + unsteady gait no sensory deficit no muscular weakness ➔ IPSILATERAL Bilateral dysfunction Lack of coordination, intention tremor, unsteady gait Key features of cerebellar lesion 1. Ataxia: Incoordination of movements 2. Intention tremor: No tremor at rest; appears on voluntary movement; Increases as task nears completion. 3. Dysmetria: Finger-nose and heel-shin tests positive 4. Dysdiadochokinesia: Disturbance in performing alternating pronation and supination in hands 5. Nystagmus: Oscillatory eye-movements when trying to track an object 6. Hypotonia & pendullar knee jerks  Divisions of Cerebellum: Summary Anatomical Phylogenetic Functional Deep nucleus Anterior lobe Paleocerebellum Spino Interposed cerebellum Primary fissure Posterior lobe Neocerebellum Cerebro- Dentate cerebellum Posterolateral fissure Flocculonodular Archicerebellum Vestibular Fastigial lobe cerebellum  26 CEREBELLAR TONSIL AND FORAMEN MAGNUM RELATION  Basal ganglia: Major components “Basal ganglia”- Island of gray matter Caudate Globus embedded in the pallidus subcortical white matter. Putamen Major components- Caudate NEOSTRIATUM CORPUS Putamen LENTIFORM STRIATUM PALEOSTRIATUM Globus pallidus NUCLEUS Subthalamic nucleus Substantia nigra  Basal ganglia: Major components contd. Caudate Internal capsule Putamen Caudate Globus Globus pallidus pallidus Thalamus Putamen Major components- Caudate NEOSTRIATUM Putamen LENTIFORM PALEOSTRIATUM Globus pallidus NUCLEUS Subthalamic nucleus Substantia nigra  Basal ganglia: Major components contd. Caudate Internal capsule Putamen Insula Globus pallidus Thalamus Major components- Caudate NEOSTRIATUM Putamen Tumors of insula such as PALEOSTRIATUM Globus pallidus glioblastoma mutiforme Subthalamic nucleus could easily invade into Substantia nigra the basal ganglia.  Coronal section Lateral ventricle Head of Caudate nucleus a. Putamen b. Globus Internal Pallidus capsule thalamus Lentiform nucleus = a + b  Transverse section Basal nuclei include: lentiform nucleus + caudate nucleus + substantia nigra Lentiform nucleus = a + b Internal a. Putamen b. Globus Pallidus capsule Thalamus Head of Caudate nucleus Neostriatum (caudate + putamen) is the “Receiving station/ input center” of basal ganglia INPUTS Cerebral cortex Striatum (striate nucleus) is the receiving station. Striatum 1. Cerebral cortex (“Corticostriatepathway”) 2. Substantia nigra compacta (“Nigrostriate pathway”) 3. Thalamus (centromedian nucleus) Thalamostriate fibers Substantia nigra compacta Globus pallidus interna and substantia nigra reticulata are the two major output stations of basal ganglia into thalamus Thalamus OUTPUTS Globus pallidus interna & Substantia nigra reticulata are the major output stations. Two pathways are: Globus pallidus interna “Pallidothalamic” and “Nigrothalamic” pathways Substantia nigra reticulata 34  Parkinson’s disease Loss of dopaminergic neurons in substantia nigra (pars compacta / nigrostriatal pathway) Characterized by Tremors (Resting tremor) Rigidity Akinesia Typically in the elderly Postural and gait disturbances Slow, stooped posture, narrow based “Festinant gait” (as though running an errand) with difficulty in initiating and stopping once begun/ “Shuffling gait”  36 Huntington’s disease (HD) Huntington’s chorea (Huntington’s disease) is often associated with degenerative lesions in the caudate nucleus; neuronal loss in striatum, cortex (frontal, parietal) HD Normal NOTE: Caudate nucleus receives inputs from the frontal association cortex. Progressive dementia and chorea (brief sudden purposeless jerks) BASAL NUCLEI PATHOLOGIES Parkinson’s disease Loss of dopaminergic neurons in substantia nigra Tremor (resting) Rigidity Akinesia Huntington’s disease neuronal loss in striatum, cortex (frontal, parietal) Progressive dementia and chorea (brief sudden purposeless jerks) age 20 to 50 yrs Hemiballismus Flailing, ballistic, undesired movements of the limbs Lesion in contralateral subthalamic nucleus Cause can be vascular or muliple sclerosis REFERENCES PRACTICE QUESTIONS ACKNOWLEDGMENT Dr Oran D. Kennedy